Combined telegraph and telephone system.



E. R. CUNNINGHAM; COMBINED TELEGRAPH AND TELEPHONE SYSTEM.

' APPLICATION FILED AUG.1'7, 1907.

976,050. Patented N0v..15, 1910.

2 snnmsgsnm 1.

THE uoRms PETERS c0, wasnma'ron, nc.

v atbo'umq E. R. CUNNINGHAM. GOMBINED TELEGRAPH AND TELEPHONE SYSTEM.

. APPLICATION FILED 11110.17, 1907. 976,050. Patented Nov. 15, 1910.

2 SHEETS-SHEET 2.

I zz 15 I i EDWARD R.

CUNNINGHAM,

on was MOINES, rown.

COMBINED TELEGRAPH AND TELEPHONE SYSTEM.

Specification of Letters Patent. Patented N 15 1919,

Application filed August 17, 1907. Serial No. 389,066.

To all whom it may concern:

Be it known that. I, EDWARD R. CUN- NINGHAM, a citizen of the United States, residing at Des Moines, in the county of Polk, State of Iowa, have invented a Com= bined Telegraph and Telephone System, of which the following is a specification.

My invention consists primarily of a method of telegraphing on an ordinary metallio telephone circuit consisting of two wires by the use of power from the 500 volt grounded trolley circuit ordinarily used on city and inter-urban electric railway lines, or from other high voltage D. C. lines, at the same time that telephones are being used on the line, and in such manner as not to interfere with the telephone service.

Certain systems have heretofore been employed for utilizing the telephone circuit along railway systems for telegraphing, the two wires of the telephone circuit being used jointly as one side of the telegraph system, whose other side is as usual made by the earth. The systems in use heretofore, however, have been what is known as series systems, their peculiarity being that each telegraph station is tapped into the line in series with the others, and according to this plan it is necessary to cut the direct connection of the telephone line and use condensers for the telephone current. The objections and difficulties :of such a system are very serious, the principal difliculties being those arising from the unbalancing of the two sides of the telephone system and the fact that all the telegraph stations are not alike, the two end ones being different from those intermediate. In my system on the contrary the telegraph instruments are introduced in parallel with each other, and all the telegraph stations are alike; and moreover any telegraph station may be cut in or out without interfering with the telephone line or with the other telegraph stations. Moreover my system is especially adapted to the use of portable instrument sets, which may be tapped in at any one of a number of plug-boxes, which are set at convenient points along the line. All this is done without cutting into or in any way interfering with telephoning or with the continuity of the telephone circuit, and in addition it is possible, where desirable, to plug in telephone instruments in place of the telegraph instruments at plug stations or both together.

One of the important features of my invention is the means whereby I procure an equal distribution of current among all the instruments on the line, and prevent the sending instruments or relays from receiving the bulk of the current, or in fact from receiving more current than any of the other instruments or relays.

Another important feature of my invention is the means whereby I provide for the use of power from the trolley or other hightension-direct current linewire, thus not only avoiding the use of portable or other batteries, but also securing better and more effective service.

My invention also embraces special and novel means for equably dividing the telegraph currents between the two sides of the telephone circuit, to cause the current on the two sides to be exactly equal and thus insure thatno telegraph current shall pass through the telephone instruments. This means consists in its most improved form of a divided impedance coil, both the ohmic and inductive resistance of which are exactly bisected at the same point; and as a further means of securing an exact balance, I may add an adjustable resistance such as a slide-wire connecting the two halves of the impedance and connected by an adjustable slide or shifting connection at such a point thereof as shall, upon listening, give a perfect silence in the telephone receiver.

My invention consists further in such constructions and combinations as will be hereinafter described, and particularly pointed out in the claims.

In the accompanying drawings I have illustrated the most approved form of my invention; and herein Figure 1 is a diagrammatic view of the connections of the circuit and instruments according to my system. Fig. 2 is a similar view illustrating a plug station having an ordinary two-point plug box and a plug with instruments connecting thereto. Fig. 3 shows one form of my divided impedance or induction balance. Fig. 4 shows diagrammatically another form thereof, with adjustable slide-wire, and Fig. 5 shows diagrammatically a third form of construction for the same.

In these drawings every reference letter and numeral refers always to the same part.

The telephone line-wires are designated a in the drawings, and the trolley or other high-tension line-wire b. The telephonewires have connected thereto at convenient points telephone-instruments A, and are tapped at the same or other points by pairs of leads 0 in each of which is placed a double-point switch OZ. Below the switch cl is placed a protector 6 with the usual ground connection f. G here and elsewhere indicates ground. Below the protector the ends of the leads 0 are connected to the opposite ends of an induction or high-resistance coil 72,. This coil 71. should be theoretically an inductive resistance; but owing to the peculiarities of my system by which I employ high-pressure sending currents, a non-inductive coil of high resistance will do almost equally well, and may be substituted.

The coil h is electrically bisected by a lead 2', so connected thereto as to exactly bisect both the ohmic and inductive resistances. This lead 11 has in successive series a resistance j, a second resistance is, and the tele graph relay m, from the last of which it passes to the ground at G. The relay m represents telegraph receiving apparatus of any preferred type or design, there being here shown as connected with it in the usual manner the sounder 'n and local battery 0.

The telegraph sending apparatus consists of the key p connected permanently by a lead 9 to the lead 2' above the resistance This key is in its preferred form, here shown, a double key, making connection whenout of use with the lead 2' below the resistance by means of a branch lead '1", and thus short-circuiting in this position the resistance j. When depressed the key ;0 makes connections with the source of current, which is in this case a tap s from a branch circuittdropped from the power line Z) to ground at G, and containing resistances u and a, respectively above and below the tap s, and so proportioned as to give the proper voltage upon the telegraph-circuit.

' As here shown the several resistances j, is,

u and o consist of incandescent lamps, though this of course is merely a matter of convenience. The resistance j is of such magnitude as to equal, or somewhat exceed, that of the line between the sending and receiving stations, and of the bisected impedances h at the two stations; thus, the resistance j of the receiving station or stations being short-circuited by the key 32, the sending-station relay will get no more current than any of the receiving relays, and the current will be equably distributed. Thus a better distribution is accomplished by the resistance but at the same time the apparatus would work, though not so satisfactorily, even with the resistance j and the short-circuiting tap 'r omitted.

The purpose of the resistance is is to procure a more even distribution of the current between the current and anumber of stations where there are more than two on the is, the same for all stations, the effect of differences in line resistance is largely nullified. This I am enabled to do by the use of the high-tension current for the telegraphcircuit as hereinabove described.

It will be noted that at a) I have shown four incandescent lamps in parallel series, which arrangement has the same resistance as a single lamp in the same position. The use of a single lamp however, would introduce the danger of throwing the entire voltage of the power line on the telephonecircuit, which would happen if the lamp elements should break. This danger is eliminated by the substitution of the four lamps as shown. It is common in electric railway service to carry a line-voltage of about 500 volts. The arrangement as shown in the drawings would therefore give a voltage on the telegraph circuit of about volts. Of course this may be varied by changing the disposition of lamps in the resistance 1), for example, if six lamps be employed (1n two series of three lamps each), the telegraph-pressure would be three elevenths of the line-pressure or 136 volts, and if two lamps in parallel were used, the telegraph-pressure would be one ninth of the line-pressure or 55 volts.

In Fig. 2 is illustrated themanner of plugging in a combined telephone and telegraph outfit, by means of an ordinary twopoint plug box D, replacing the switch cl. The box D has terminals cZ, (Z to which are connected the leads from the telephone line, and an ordinary two-point plug (Z carrying the opposite poles of the leads 0 and making connection with the respective terminals. Between the protector e and impedance-coil h are connected to the leads 0' the branch leads w of the telephone set w. Otherwise the arrangement is the same as shown in Fig. 1.-

It will be seen that these arrangements cannot interfere with the telephone currents which are of an oscillatory nature and there fore cannot pass through the impedance h. This impedance, however, ofiers no resistance to the passage of the telegraph-cun rents, since these currents pass in opposite directions in the two halves thereof, consequently the induction of one half nullifies that of the other. It is highly important, however, that the telegraph-current shall be exactly evenly divided between the two sides. of the telephone-circuit, otherwise the ticking of the instruments would produce noises in the'telephones. This is easy to accomplish if the coil 72. is non-inductive, because it merely means finding the proper bisectingpoint of the resistance of the coil. But

where, as ordinarily and preferably, the coil it is inductive, it is necessary to perfect working that the ohmic and induction centers should be at the same point, since the impedance of the coil is made up of these two factors, and if not so divided the impedance of the two sides would be dephased, so as to result in pulsating currents and resulting noises in the telephone-circuit from the tele graph currents. Now in an ordinary coil the ohmic center is not at the same point as the induction center, because the former divides the length of wire in two equal parts, and the latter the number of turns, whereas the turns are of different lengths so that the number of turns in one half would have a greater or less resistance than the same number of turns in the other. In Fig. 3 is shown one means of overcoming this difficulty. In this construction I provide twin coils 11, mounted on a single core 12 and inclosed in the same magnetic box or casing 13. The coils themselves are wound alike, with the same total length of wire and the same number of turns in each, consequently their resistance is the same, and as they are mounted on the same core their inductance will also be the same. then connected to the outer ends of the two coils, and their inner ends being joined and connected to the lead 2', the desired result will be secured.

7 Another method, and perhaps a preferable one in that it admits of an exact adjustment of one of the two factors of impedance, is shown in Fig. l. Two separate coils 14; are here represented in section, each having a magnetic core 15 and casing 16, comprising the magnetic circuit, and a wire-coil 1? wound upon the core; both coils 17 having the same number of turns and being otherwise as nearly as possible alike. The inner end of one coil and the outer end of the other are now connected to one side of the telephone-circuit a, and the outer end of the first and inner end of the second are connected to the other side, as shown. At a point 18 in each coil, bisecting the number of turns, a tap 19 is brought out to a terminal 20, and the two terminals 20 are connected together by a high resistance 21. The lead 71 to the telegraph-instruments is connected to the wire 21, and a sliding-contact 22 is provided, which may be adjusted in use until the requisite balance between the two sides of the telephone-circuit is perfectly secured. It is to be observed that the telegraph currents are divided at 22- into two parts, and at 18 each half is again divided into two parts, these latter being unequal because the resistance of the inner half of the coil is less than that of the outer half; but the current through the inner half of one coil and the outer half of the other goes to one telephone wire, and the current The leads 0 being resistance. two middle ends by the conductor 26, the latthrough the outer half of the first coil and the inner half of the second goes through the other telephone wire a. In this manner an equalization is secured, and any inequality between the two coils is compensated by adjusting the slide 22.

In Fig. 5 is shown still another means of accomplishing the same end. 23 here designates a magnetic core, and 24: the inclosing casing. On the core 23 is wound a double coil consisting of two wires of equal section and specific resistance, these being designated 2 1 and 25, and being shown in an open spiral in the figure for the purpose of enabling them to be distinguished. Being wound simultaneously the two wires will have the same length and the same number of turns, consequently the same resistance and inductance. The outer end. of one wire and the inner end of the other are now connected to the opposite sides of the telephone circuit a by means of the leads 0 as heretofore, while the inner end of the first and the outer end of the second are connected together by a conductor 26, which is in turn connected to the telegraph-circuit 2'. It is clear that this arrangement will have the desired effect, since the two halves are connected in series as regards the telephone-circuit and in parallel as regards the telegraph circuit, and are equal both in inductance and Instead of joining together the ter might be replaced by a slide-wire arrangement as in Fig, 1.

While I have hereinabove described the preferred form of my system and all those features which conduce to the greatest perfection, I do not wish it understood that my invention is restricted to the use of all of said features, or of said features in the exact form and arrangement shown, as some of those may be omitted or altered, as will readily occur to those skilled in the art.

In the following claims the word impedance, where not otherwise qualified, is to be construed broadly, as being made up of resistance and inductance in any proportion, or including either of these two factoiswithout the other.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

V 1. In combination with a metallic telephone-circuit, an impedance connecting the two sides thereof, a lead connecting the electrical center of said impedance with the ground, telegraphic-receiving devices in said lead, a high-tension line-wire, a connection between said line-wire and said lead, and a sending-key in said connection.

2. In combination with a metallic-telephone-circuit, a high-tension line-wire, an impedance connecting together the two sides of said telephone-circuit, a lead connecting the electrical center of said impedance with the ground, telegraphic receiving devices in said lead, a connection between said linewire and said lead above said receiving devices, and a sending key in said connection.

3. In combination with a metallic telephone circuit, a high-tension line-wire, an impedance connecting together the two sides of said telephone-circuit, a lead connecting the electrical center of said impedance with the ground, telegraphic receiving devices in said lead, a resistance in said lead in series with said receivingdevices, a connection from said lead at a point above said resistance and receiving devices to said line-wire, and a sending-key in said connection.

4. In combination with a metallic telephone-circuit, an impedance connecting the two sides thereof, a lead connected at one end to the electrical center of said impedance and at the other to a common conductor such as the ground, a resistance and a telegraphicreceiving device in series in said lead, a source of electric current, and a key connected with said lead above and below said resistance and with said source of electric current so as to short-circuit said resistance and in sending to introduce current above said resistance.

5. In combination with a metallic telephone-circuit, an impedance connecting the two sides thereof, a lead connecting the electrical center of said impedance with a common conductor such as the ground, two resistances and a telegraphic-receiving device in said lead, a source of electric current, a double key connected at all times to said lead above the first resistance, a connection from said lead between the two resistances to said key and electrically connected with said key when it is not in use and disconnected therefrom when said key is operated to send a message, and a connection from said source of ener y to said key connecting with the latter when it is operated to send a message.

6. In combination with a telegraph-circuit, means for energizing the same comprising a high-tension line-wire, a connection to said line-wire across the high-tension circuit, two resistances in series containing said connection, one of said resistances comprising a plurality of incandescent lamps in series and the other comprising a plurality of incandescent lamps in parallel series, a connection from a point between said resistances to said telegraph-circuit, and a sending key in said connection.

7. In combination with a metallic telephone-circuit, an impedance connecting the two sides of said circuit, a lead connected at one end to the'electrical center of said impedance and at the other end to a common conductor such as the ground, two resistances and a telegraphic receiving device in series in said lead, a high-tension line-wire,

a branch circuit from said line-wire to said common conductor, two resistances-in series in said branch circuit, a sending-key connected constantly to said lead above said first-named resistances, a connection from said lead between said two first-named resistances to said key, the latter normally short-circuiting one of the resistances, and a connection from between said two resistances in said branch-circuit to said key and adapted to supply currents to the telegraph-circuit at a point in said lead above said firstnamed resistances when said key is operated to send a message.

8. In combination with a metallic telephone-circuit, an impedance connecting the two sides of said circuit, a lead connected at one end to the electrical center of said impedance and at the other end to a common conductor such as the ground, two resistances and a telegraphic-receiving device in series in said lead, a high-tension line-wire, a branch-circuit from said line-wire to said common conductor, two resistances in series in said branch-circuit a sending-key connected constantly to said lead above said first-named resistances, a connection from said lead between said two first-named resistances to said key, the latter normally short-circuiting one of said resistances, and a connection from between said two resistances in said branch-circuit to said key and adapted to supply currents to the telegraphcircuit at a point in said lead above said first-named resistances when said key is operated to send a message; the resistance in said branch-circuit below said key-connection comprising a plurality of incandescent lamps in two or more parallel series.

9. In a combined telephone and telegraph system, the combination of a pair of linewires forming together a telephone-circuit, an inductive impedance connecting said Wires, said impedance being divided into two parts approximately equal both as to induction and as to resistance, a balancing resistance connecting the two parts, a lead containing telegraphic apparatus and forming one side of a telegraph circuit, and means electrically connecting said lead with said balancing resistance and shiftable to diiierent points thereon whereby an electrical balance is obtained.

10. In a combined telephone and telegraph system, the combination with a pair of line-wires forming together a metallic telephone circuit, an inductive impedance connecting said wires, said impedance being dividedinto two parts having the same length and specific resistance and the same number of turns about a magnetic core, a balancing resistance connecting theadjacent ends of said impedance, and a lead forming part of a telegraph-circuit and having an adjustable connection with said halancing resistance whereby the exact electrical center may be found.

11. In combination with a pair of linewires forming opposite sides of the same circuit and forming together the same side of a second circuit, a divided impedance comprising a pair of substantially equal coils spirally wound and having substantially equal numbers of turns, lengths, resistances, and magnetic circuits, connections between the respective line-wires and the respective ends of the two coils, one line-wire being connected to the inner end of one coil and the outer end of the other, and the second line-wire the reverse, a balancing resistance connecting the inductive center of one coil with the inductive center of the other, a lead forming part of a second circuit, and a slidingconnection adapted to connect said lead electrically with any part of said balancing resistance.

12. In a combined telephone and telegraph system, the combination with a pair of line-wires forming together a metallic telephone circuit, a balancing resistance, and an inductive impedance connecting said wires, said impedance being divided into two parts having the same length and specific resistance and the same number of turns about a magnetic core, and connected to said balancing resistance, the latter being variable on one side of the system.

13. In combination with a pair of linewires forming opposite sides of the same circuit and forming together the same side of a second circuit, a divided impedance comprising a pair of substantially equal coils spirally wound and having substantially equal numbers of turns, lengths, resistances, and magnetic circuits, connections between the respective line-Wires and the respective ends of the two coils, one line-wire being connected to the inner end of one coil and the outer end of the other, and the second line-wire the reverse, and a lead forming part of a second circuit connected to the inductive center of both coils.

In witness whereof, I have hereunto set my hand this 14 day of August, 1907.

EDWARD R. CUNNINGHAM.

\Vitnesses E. B. BIEGHLER, FRANK C. TATE. 

